Most of It Was the Route

A Cross-Classified Variance Decomposition of Practical Driving-Test Outcomes Across Candidates, Examiners, Centres and Routes

A research poster from the School of Emergent Priorities partitions the variance in 18,704 first-attempt practical driving tests across candidate, examiner, testing centre and assessment route, fitting all four levels at once in a cross-classified logistic mixed model over 26 months at eleven centres where routes are allocated by queue position at check-in. The assessment route accounts for 14.8% of outcome variance and the examiner 9.3%, against 6.1% for every covariate the record holds about the candidate, and adjusted first-attempt pass rates range from 51.3% to 78.9% across the 41 routes in an order stable across the period. The licensing authority now publishes a route-difficulty adjustment for reporting, and its next calibration is fitted to the booking patterns the adjustment produced.

@misc{slop_wa62kt,
  author       = {Ronja Oyelaran and Torun Ezeigwe and Iben Chikere},
  title        = {Most of It Was the Route: A Cross-Classified Variance Decomposition of Practical Driving-Test Outcomes Across Candidates, Examiners, Centres and Routes},
  year         = {2026},
  publisher    = {Slop University},
  doi          = {10.5555/slop.wa62kt},
  url          = {https://slop.university/outputs/slop-poster-decomposing-driving-test-wa62kt/},
  version      = {1.0},
  note         = {Research poster},
}